Iron and cobalt are the central metal ions in many complexes that participate in oxidation or reduction catalysis in living systems and in various commercial applications. The heme proteins are examples. In this research, attention will be focused on the ways in which the oxidation-redution properties of iron and cobalt respond to carefully controlled variations in the structures of macrocyclic tetradentate ligands to which they are bound. Many of the ligands will also have superstructures associated with them. Pertinent properties include standard electrode potentials, reversibility of electrode reactions, availability and stability of extreme oxidation states and ability of the compound to function in the appropriate reaction; e.g., decompose hydrogen peroxide, oxidize a substrate, form a complex with molecular oxygen. Superstructured complexes involve appended structural components that are present to serve additional purposes beyond coordination to the metal. Such superstructures are appended in systems of interest in order to shelter a bound ligand from ambient conditions, inhibit or distort the mode of binding of a small ligand, promote the reaction of a bound ligand, or accommodate a substrate near an active site.